GAMS error codes

Note

In brief — A quick-reference guide to the GAMS errors most commonly seen when running OPEN-PROM, separating compile-time errors (including domain violations) from execution-time solver and model-status issues and from licensing problems, with the likely cause and fix for each.

Encountering errors while working with GAMS is common, but knowing how to troubleshoot them saves time. This page summarises the errors most frequently met when running OPEN-PROM. It keeps two distinct categories apart: compile-time errors, which GAMS reports with a numeric **** NNN code while reading the model, and execution-time solver and model-status issues, which the solver reports (or which appear in the solve summary) only after compilation has succeeded. Licensing problems are listed last.

Compile-time errors

Compile-time errors occur while GAMS reads (compiles) the model, before any solve. To locate them, search for four asterisks (****) in the .lst file generated by GAMS.

Tip

The **** marker always sits at the start of the line where GAMS flags a problem, so a plain text search through the .lst file is the fastest way to jump to the offending statement.

Code	Message	Cause	Fix
101	Syntax error, unexpected keyword in the declaration of a component	A syntax error in the GAMS code.	Double-check the syntax and make sure all keywords are spelled correctly.
102	Symbol `xxx` already defined	A symbol is defined more than once.	Check for duplicate definitions of symbols (variables, equations, parameters) and ensure each is defined only once.
103	Inconsistent equation definition	Inconsistencies in the definition of equations.	Review the equations and ensure they are correctly defined for the problem at hand.
170	Domain violation for element	A set element is referenced that is not a member of the set declared for that index position — a typo, an element missing from the set declaration, or an external label that does not match the domain (for example a year header in an input CSV that does not match a `YTIME` label).	Check the referenced labels against the declaring set, and make sure external data (CSV headers and similar) use exactly the labels GAMS expects.
171	Domain violation for set	The wrong set, or sets in the wrong order, is used for an index position (for example writing `d(j,i)` when `d` was declared over `(i,j)`).	Verify that each index uses the correct declaring set and that the indices appear in the declared order.

Tip

Error 170 is the one most often hit in the soft-link workflow: year column headers in iPrices_magpie.csv must be bare integers (2010,2011,…) so they match OPEN-PROM’s YTIME labels — a y prefix or an out-of-range year triggers a domain violation. See Soft-linking.

Execution-time solver and model-status issues

The conditions below are not compile-time **** NNN codes. They are reported by the solver (CONOPT) or appear in the solve summary as MODEL STATUS / SOLVE STATUS only after compilation has succeeded, so they are diagnosed differently from the codes above.

Pre-triangular infeasibility. Before its main iterations, CONOPT solves the recursively-determined (pre-triangular) part of the model. It reports a pre-triangular infeasibility when a variable forced by this part cannot meet its bounds. In OPEN-PROM this is frequently a numerical artefact of an over-tight triangular feasibility tolerance rather than a genuinely infeasible model; relaxing CONOPT’s Tol_Feas_Tria (triangular feasibility tolerance), or revising the initial values and bounds, usually clears it.

Model infeasible. A MODEL STATUS of infeasible means no point satisfies all constraints. Review the constraints and objective for conflicting or overly restrictive conditions; the listing flags the rows that are infeasible at the reported solution, which is the place to start.

License errors

“The installed license is invalid” / “License has expired”. Ensure that the gamslice.txt file inside the installation bin folder is correct and holds valid license information.

Warning

GAMS does not always read the license file from the bin folder. Check the file path quoted in the error message to confirm which license file GAMS is actually referencing.

General troubleshooting tips

Check log files. Review the GAMS log files for detailed error messages and diagnostic information.
Consult the documentation. The GAMS documentation and user guides explain error messages and offer troubleshooting advice.
Update the GAMS version. Newer versions may include bug fixes and improvements relevant to the error.
Search forums and communities. Solutions to common GAMS errors are often found in online forums; otherwise, post your question to seek help from experienced users.